Connector for expandable well screen

ABSTRACT

A tubing connection arrangement ( 10 ) comprises two expandable tubing sections ( 12, 14 ), each tubing section comprising a filter screen ( 16, 18 ) sandwiched between inner expandable tubing ( 20, 22 ) and outer expandable tubing ( 24, 26 ). The filter screen of one tubing section overlaps the filter screen of the other tubing section and the outer expandable tubing of at least one of the tubing sections extends over the overlapping filter screens. On expansion of the tubing sections, the overlapping filter screens, restrained by the outer tubing, ensure the integrity of the filter between the tubing sections.

This invention relates to a downhole connector, and in particular to anarrangement for ensuring the integrity of a sand screen or other filtermedium at a connection between two lengths of expandable tubing utilisedto support or form a sand screen or filter.

In many well bores where a liquid, for example oil, passes from asurrounding formation into the well bore, the liquid will often carryentrained sand particles. If this sand is permitted to pass into thewell bore a number of problems may arise, including an increasedlikelihood of the well bore becoming blocked or restricted, and the sandmay cause downhole tools to stick or jam, or wear prematurely.Accordingly, it is preferred that the sand particles are retained in theformation. This is achieved by providing screens or a filter around thecasing or production tubing.

International Patent Application WO 97/17524 (Shell), the disclosure ofwhich is incorporated herein by reference, describes a radiallyexpandable assembly in which overlapping filter sheets are sandwichedbetween inner expandable support tubing and outer expandable protectivetubing, the expandable tubing featuring large numbers of overlappinglongitudinal slots. When an expander cone is forced through theassembly, the inner and outer tubing is expanded radially, the slotsextending to form diamond-shaped openings. The initial degree of overlapbetween the screens is selected such that, although the screens movecircumferentially relative to one another during expansion, the edges ofthe screens remain in overlapping relation. Such an arrangement caneasily be constructed over sections of plain tubing or pipe. However, atthe connections between tubing sections, where the inner tubing sectionsare coupled together, it is difficult to maintain a “sand-tight” join.

It is among the objectives of embodiments of the present invention toprovide a connector arrangement which obviates or mitigates thisdifficulty.

According to the present invention there is provided a connectorarrangement for provision between the ends of two sections of expandabletubing, each expandable tubing section comprising a filter screensandwiched between inner expandable tubing and outer expandable tubing,the filter screen of one tubing section overlapping the filter screen ofthe other tubing section and the outer expandable tubing of at least oneof the tubing sections extending over the overlapping filter screens.

The invention also relates to expandable tubing sections which areadapted to be connected in this manner, and to expandable tubing stringsincorporating such connector arrangements, and to a method of connectingtubing sections.

On expansion of the tubing sections, the overlapping filter screens,restrained by the outer tubing, ensure the integrity of the filterbetween the tubing sections.

The outer expandable tubing of one tubing section may be arranged tooverlap or to bust against the outer expandable tubing of the othertubing section.

Each filter screen will typically comprise a plurality of overlappingplates, sheets or membranes individually mounted to the respective innerexpandable tubing by axially parallel connectors or fixings, such asscrews, lugs or welds.

Preferably, the filter screens of each tubing section are initiallyradially spaced apart to facilitate make-up of the connector. However,on expansion, the resistance of the outer tubing to radial expansion ofthe inner tubing ensures that the outer filter screen is pressed intosand-tight engagement with the inner filter screen. The desired relativepositioning of the filter screens of the two tubing sections may beachieved by providing one inner tubing section having an end of slightlylarger diameter than the other. In certain embodiments the ends of eachtubing section may be upset, that is of greater diameter than theremainder of the tubing section, and the desired difference in diametermay be achieved by providing a slightly higher upset on one tubingsection. Conveniently, the inner tubing sections will feature pin andbox connections, and the upset on the box may be slightly higher thanthe pin. Of course the opposite arrangement may provided, that is thepin upset being higher than the box.

The ends of one or both filter screens may be provided with means forpreventing interference between the screen ends when the tubing sectionsare rotated relative to one another, as may be the case if the tubingsections are threaded to one another. Said means may take the form of asleeve of flexible or extendible material located internally and\orexternally of the filter screens. The sleeve may be formed of flexibleslotted tubing, plastics, rubber, wire mesh or wire composites.

According to another aspect of the present invention there is provided asection of expandable tubing comprising a filter medium sandwichedbetween inner expandable tubing and outer expandable tubing, the filtermedium comprising a plurality of circumferentially extending filtersheets, each sheet being coupled at one edge to one of the inner andouter tubing and having the opposite edge overlapping an adjacent sheet,and means for reducing the friction between at least one of the filtersheets and the filter sheets and the tubing.

In other aspects of the invention friction reducing means may beprovided on other parts or elements of a tubing section.

This aspect of the invention may be provided in combination with thefirst described aspect.

In use, the friction reducing means facilitates expansion of the tubingby facilitating relative circumferential movement of the filter sheetsrelative to one another and of the filter sheets relative to the tubing.The presence of such friction reducing means also reduces the likelihoodof damage occurring to the relatively fragile filter sheets duringexpansion, as has been found to occur on occasion in tubing made inaccordance with WO 97/17524.

Preferably, the friction reducing means is a low friction coatingapplied to the filter sheets, such as a PTFE-based material such asTeflon (trade mark). In other embodiments a friction-reducing lubricant,such as high temperature grease, may be provided. Alternatively, sheetsof low friction material may be placed between the filter sheets and thetubing.

These and other aspects of the present invention will now be described,by way or example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic sectional view of part of a connector inaccordance with a preferred embodiment of the present invention, withthe connector parts shown separated; and

FIG. 2 is a schematic sectional view of the connector of FIG. 1, withthe connector parts shown coupled together.

The drawings illustrate part of a connector 10 in accordance with anembodiment of the present invention. The connector 10 is providedbetween the ends of two sections of expandable tubing 12, 14, eachcomprising filter plates 16, 18 sandwiched between inner expandablesupport tubing 20, 22 and outer expandable protective tubing 24, 26.Each section of expandable tubing 20, 22, 24, 26 defines a large numberof longitudinal overlapping slots. The sections of inner or baseexpandable tubing 20, 22 are formed with co-operating pin and boxconnections 28, 30, to allow the tubing sections 12, 14 to be made up byrelative rotation.

As is more clearly apparent from FIG. 2, the box connection 30 is upsetfrom the pin 28. The filter plates 18 mounted around the box 30 extendbeyond the end of the box outer surface 32 such that on making up theconnection the filter plates 18 overlap the filter plates 16 mounted onthe pin 28. The outer tubing 24 on the pin 28 terminates short of theend of the filter plates 16 to accommodate the filter plate overlap, andthe outer tubing 24 is similarly overlapped by the end of the outertubing 26 on the box 30.

The overlapping filter plates 16, 18 are positioned such that there is asmall radial gap G between the filter plates 16, 18, to allow theconnection to be made up without snagging or galling of the opposingfilter plates.

When the connection is expanded downhole, by passing a cone through theconnection, the outer tubing 24, 26 resists the expansion of the innertubing 20, 22. This results in the outer tubing 24, 26 providing aninward radial force which maintains the overlapping filter plates 16, 18in engagement and effects a sand-tight seal.

To facilitate make-up and backing-off of the connection 10, the ends ofthe filter plates 16 are provided with an expandable make-up protectionsleeve 32 which prevents the overlapping plates on either the pin 28 orthe box 30 from snagging on the opposing filter plates when the pin andbox are rotated relative to one another.

To facilitate expansion of the tubing, the filter plates 16, 18 areprovided with a coating 34 of a low-friction material, in this case aPTFE-based material such as Teflon. This coating facilitates relativemovement of the plates 16, 18, and relative movement of the plates 16,18 and the tubing 20, 22, 24, 26, and minimises the risk of tearing ofthe filter plates 16, 18 as the tubing sections are made up andexpanded.

It will be clear to those of skill in the art that the above-describedembodiment is merely exemplary of the present invention, and thatvarious modifications and improvements may be made thereto withoutdeparting from the scope of the present invention.

What is claimed is:
 1. A tubing connection arrangement comprising twoexpandable tubing sections, wherein each tubing section comprises afilter screen sandwiched between an inner expandable tubing and an outerexpandable tubing, wherein the filter screen of one tubing sectionoverlaps the filter screen of the other tubing section, and wherein theouter expandable tubing of at least one of the tubing sections extendsover the overlapping filter screens.
 2. The arrangement of claim 1,wherein the outer expandable tubing of one tubing section is arranged tooverlap the outer expandable tubing of the other tubing section.
 3. Thearrangement of claim 1, wherein the outer expandable tubing of onetubing section is arranged to butt against the outer expandable tubingof the other tubing section.
 4. The arrangement of claim 1, wherein eachfilter screen comprises a plurality of overlapping sheets individuallymounted to the respective inner expandable tubing by axially parallelfixings.
 5. The arrangement of claim 1, wherein the filter screen of onetubing section is initially of greater diameter than the filter screenof the other tubing section such that the filter screens are initiallyradially spaced apart.
 6. The arrangement of claim 5, wherein the innertubing of said one tubing section has an end of larger diameter than theend of the inner tubing of the other tubing section.
 7. The arrangementof claim 6, wherein the ends of at least one tubing section are upset.8. The arrangement of claim 7, wherein the ends of both tubing sectionsare upset, with a higher upset being provided on one tubing section. 9.The arrangement of claim 7, wherein the inner tubings incorporate pinand box connections, and the upset on the box is higher than the upseton the pin.
 10. The arrangement of claim 1, wherein the end of at leastone filter screen is provided with means for preventing interferencebetween the screen ends when the tubing sections are rotated relative toone another.
 11. The arrangement of claim 10, wherein said means forpreventing interference is a sleeve of extendible material.
 12. Thearrangement of claim 11, wherein the sleeve extends internally of atleast one of the filter screens.
 13. The arrangement of claim 11,wherein the sleeve extends externally of at least one of the filterscreens.
 14. The arrangement of claim 1, wherein the filter screencomprises a plurality of circumferentially extending filter sheets, eachsheet being coupled at one edge to one of the inner and outer tubing,having the opposite edge overlapping an adjacent sheet, and being coatedwith a low friction coating configured for reducing the friction betweenat least one of the filter sheets and the tubing.
 15. The connection ofclaim 1, wherein the expansion resistance member comprises a sleeve. 16.The connection of claim 15, wherein the sleeve substantially surroundsthe connection.
 17. A tubing connection method comprising: providing atleast two expandable tubing sections, each tubing section comprising afilter screen sandwiched between an inner expandable tubing and an outerexpandable tubing; and connecting the tubing sections such that thefilter screen of one tubing section overlaps the filter screen of theother tubing section and the outer expandable tubing of at least one ofthe tubing sections extends over the overlapping filter screens.
 18. Asection of expandable tubing comprising: two filter screens sandwichedbetween an inner expandable tubing and an outer expandable tubing, eachfilter screen comprising a plurality of circumferentially extendingfilter sheets, each sheet being coupled to the inner expandable tubingand coated with a low friction coating configured to reduce the frictionbetween the filter sheets.
 19. The section of claim 18, wherein the lowfriction coating is made from a polytetrafluoroethylene-based material.20. The section of claim 18, wherein the low friction coating is furtherconfigured to reduce the friction between at least one of the filtersheets and the outer expandable tubing.
 21. An expandable connector forconnecting portions of expandable tubing comprising: a first connectorportion and a second connector portion, the first and second portionsbeing threadably engaged to one another; an outer tubular member forsurrounding a portion of the threadably engaged first and secondportions and resisting a radial expansion thereof; and a filter screenhaving a plurality of circumferentially extending filter sheets, whereineach sheet is coupled to one of the first connector portion and secondconnector portion at one edge and overlaps an adjacent sheet at theopposite edge.
 22. An expandable connection for well bore tubulars,comprising: a first well bore tubular having a first connection member:a second well bore tubular having a second connection member; whereinthe first connection member is threadably engaged with the secondconnection member to form the expandable connection; an expansionresistance member disposed outside the expandable connection forresisting the expansion of the expandable connection; and a filterscreen having a plurality of circumferentially extending filter sheets,wherein each sheet is coupled to one of the first connection member andthe second connection member at one edge and overlaps and adjacent sheetat the opposite edge.
 23. A method of expanding a wellbore tubular,comprising: providing a wellbore tubular having a first connectionmember threadably engaged with a second connection member and anexpansion resistance member disposed therearound; and expanding thefirst and second connection members radially outward against an inwardradial force provided by the expansion resistance member, the first andsecond connection members remaining threadably engaged during and afterexpansion.
 24. An expandable connector for connecting portions ofexpandable tubing, comprising: a first connector portion and a secondconnector portion, the first and second portions being inter-engageableand expandable to produce a larger diameter connection between theportions that remains inter-engageable; and an outer tubular member forsurrounding a portion of the inter-engaged first and second portions andfor resisting the radial expansion thereof.
 25. The connector of claim24, wherein the outer tubular member is expandable.
 26. The connector ofclaim 24, wherein the first connector portion and the second connectorportion are engaged by a threaded connection.
 27. A method of expandinga tubular connection, comprising: providing a first connection portionengaged with a second connection portion; providing an outer memberpartially surrounding the engaged portions; and expanding the engagedportions radially outward, thereby causing the outer member to expandwhile resisting a radial expansion force exerted by the engaged portionswhereby the first connection portion and the second connection portionremain engaged after expansion.
 28. The method of claim 27, wherein thefirst and second portions are engaged by a threaded connection.
 29. Themethod of claim 27, wherein the outer member expands as a result of theengaged portions being expanded radially outward.
 30. An expandableconnection for expandable tubulars, comprising: a first expandabletubular having a first connection member; a second expandable tubularhaving a second connection member engaged with the first connectionmember, wherein the first and second connection members are expandable,and the first and second connector members remain engaged followingexpansion thereof; and an outer tubular member surrounding a portion ofthe engaged first and second connection members, wherein the outertubular member is configured to expand in response to the first andsecond connection members being expanded.
 31. A method of expanding atubular connection comprising: providing a first connection portionengaged with a second connection portion, the portions being expandable;and expanding the portions radially outward while applying a force fromwithout the tubular connection, wherein the force opposes the expansionand causes the engagement to retain integrity following the expansion.